In the field of medical technology, the cathode ray tube (CRT) display has become an indispensible item as a vehicle for visually presenting the results of both real time and previously conducted activities in such fields as microscopy, X-ray analysis, magnetic resonance imaging, digital subtraction angiography, radio isotope imaging, computed tomography, nuclear medicine and sonography, to name a few. In each case, use is made of a video signal derived from an array of sensors specifically designed to detect certain physiological aspects of the human body.
Video imaging systems are also used in other fields of analysis such as surveillance, radar scopes, aerial photo interpretation, ultrasound diagnosis, stress analysis, nuclear magnetic resonance, fingerprint analysis, to name a few. In all of these fields, the CRT display typically takes the form of a monochrome display that reproduces images in what is commonly known as black-and-white or monochrome mode. In situations where a color monitor is employed, color is introduced as a means of distinguishing between contrasting features found in the displayed image. In certain prior art devices, color is introduced through pre-processing circuitry which detects the variable intensity of the features of an image as monitored by a sensor and then assigns a color to that feature based on the recorded intensity. The assigned color is selected by the manufacturer and the user has no ability to alter that color because the diagnostic technique developed around the machine requires that certain colors be reproduced.
There is thus a need for an imaging system which is capable of reproducing both the conventional black-and-white images as well as the color images and, at the same time, provide the user with the ability to selectively introduce color elements into the normally monochrome image provided by either the monochrome or composite video signal derived from the prior art machines.